London landmarks join thousands of others around the world that will go dark for an hour to raise awareness about climate change

At 8:30pm today the luminous face of Big Ben will go dark. Next door, the houses of parliament will switch off all its lights too, along with thousands of landmarks, buildings and people around the world in a global gesture of solidarity in the fight against climate change.

From the international dateline, Earth Hour starts in New Zealand’s Chatham Islands and will conclude in Honolulu. Passed like a baton around the planet, cities including Sydney, Hong Kong, Singapore, Moscow, Istanbul, Dubai, Cape Town and Las Vegas will be darkened for an hour at 8:30pm local time to mark Earth Hour, the single biggest mass event to mark public concern over global warming.

More than 3,200 cities across 88 countries have signed up and the event has received support from international leaders including Archbishop Desmond Tutu and the United Nations secretary general, Ban Ki-moon. Environment campaign group WWF, which is co-ordinating the global event, expects hundreds of millions of people around the world to take part in turning out their lights for an hour, in the hope of sending a direct message to world leaders that their voters want urgent action to save the planet from rising temperatures.

“Earth Hour is shaping up to be an impressive symbolic response to our planet in peril,” said the climate change secretary, Ed Miliband, who is supporting the event. “Popular pressure like this will leave little doubt around the negotiating table in Copenhagen this December that a meaningful global carbon deal must be delivered. Making us all more aware of the energy we use is a critical first step in making lasting changes to our lifestyles.”

The Eiffel Tower, Shanghai’s Hong Kong New World Tower, the Christ the Redeemer statue in Rio de Janeiro, Sydney’s Opera House and Table Mountain in Cape Town will all take part.

In London, Nelson’s Column, City Hall, the National Gallery and the National Theatre will switch off their lights. The Millennium Stadium in Cardiff, the Clifton suspension bridge in Bristol, the Belfast Wheel and Scotland’s Forth rail bridge and Edinburgh castle will all go dark.

Over 1,200 schools in the UK have also been active in the run-up to Earth Hour, with pupils receiving lessons on the challenges faced by climate change. WWF’s head of campaigns, Colin Butfield, said the idea was that children would then go home and pester their parents to turn out lights . Members of the Women’s Institute have also been encouraged to support the event at home.

Almost 400 British businesses are also taking part. Furniture retailer Ikea will turn off the lights outside its stores while Coca-Cola will switch off its advertising screen at Piccadilly Circus, only the third time it has been extinguished since the second world war.

“We hope it communicates the importance of everybody being involved in this and hopefully this will increase awareness that everybody needs to do their part, that includes governments, NGOs and individuals,” said Coca-Cola’s Euan Wilmshurst.

Green electricity company, Good Energy, has written to its 25,000 customers, encouraging them to turn out their lamps and light candles for an hour instead. Founder and chief executive Juliet Davenport encouraged people at home to play candle-lit board games and said that mass events such as Earth Hour allowed people to see how small actions, of the kind needed to tackle climate change at an individual level, could add up to something influential on a global scale.

The idea for Earth Hour grew out of a similar campaign held by WWF’s Australian campaigners in 2007. For the global version, the campaign group chose 2009 because of the negotiations in Copenhagen to set climate targets after the Kyoto protocol runs out in 2012.

Campaigners have not calculated the amount of energy that might be saved by the combined action around the world, arguing that Earth Hour is more symbolic than a direct attempt to save carbon emissions.

“When global leaders meet at the UN conference in Copenhagen later this year, they are going to determine how the world will work together to tackle climate change in future. We need them to know that the eyes of the world will be upon them,” said Butfield. “Earth Hour is a simple way for people all over the world to make sure our leaders really understand that people are looking to them to do what is right and that the time for action is now.”

Not everyone is so positive, however. Organisers had hoped for the participation from the Forbidden City in Beijing but Chinese government officials have told their citizens to hold back because Earth hour clashes with Serf Liberation Day in Tibet, a new holiday to commemorate the ousting of the Dalai Lama from the province.

George Marshall, of the charity Climate Outreach and Information Network, questioned whether darkness was the right symbol. “This action offers darkness, regression and the threat of less. Light has always been a symbol of progress, civilisation, intelligence, truth. Turning off lights has always been a symbol of collapse ‑ the Dark Ages.”

But Andy Ridley, of WWF in Australia, said: “For the people who take part, we hope there is a sense of empowerment, the knowledge that however small or big the actions you can effect in your life, whether you are a CEO or doing your GCSEs you can make a difference when these actions are brought together.”